It can be advantageous in the design of electronic devices, portable or otherwise, to implement techniques to reduce power consumption. With reduced power consumption, advantages can be obtained such as prolonged battery life (where batteries are used), reduced thermal generation, and less real-estate required for power supplies. Portable electronic devices such as cellular telephones, PDAs, laptop computers, wireless network devices and so on, can benefit from techniques for reducing power consumption.
One effective method to reducing power consumption is to enable devices to go into a sleep or hibernation mode when not in use. In such modes, devices may turn off entirely, or turn off or cut back certain functions, until the device is called upon for activity. Thus, terms such as hibernation, power-save mode, sleep mode, or inactive, are used somewhat interchangeably herein to refer to complete or partial shutdown of devices and their components.
Timers, user input, communications, or other events may trigger full or partial awakening from a sleep mode. For example, with hand-held devices that have human interfaces, the pushing of a button or other user action might be sufficient to waken the device from a power-save state. However, where a device might be called upon for action without human interaction, such as for example, a communication device, techniques other than user input are useful for wakening the device.